1. Field of the Invention
The present invention relates to an internal weld joint cleaner, and more particularly, to a weld joint cleaner designed to travel within an internally coated pipeline and clean the interior of said pipeline in the cutback area which surrounds the weld joint and extends up to a point where previously applied internal coating ceases, such area being filled with flux and residue from welding two pipe joint sections together.
2. Prior Art
The present invention relates to a pipeline which is made up from pipe sections which have been previously coated at the mill except for the ends thereof which are left uncoated so that the sections can be welded together in the field in an end-to-end relation. In this particular case, we are concerned with a pipeline which is internally coated; that is each pipe section is previously internally coated except for a band extending about 4-8 inches back from the end of each pipe section. This band is sometimes referred to as the cut-back area. Thereafter, the pipe sections are welded together in the field which means that there will be a total area of 8-16 inches of bare or uncoated pipe around each weld joint which must be cleaned prior to the application of a coating over the weld joint. The added coating will overlap with the internal coating which has been previously applied at the mill.
A machine for coating the uncoated weld joints in an otherwise internally coated pipeline is disclosed in Hart U.S. Pat. No. 4,092,950 issued on June 6, 1978; however, in order to effectively employ the apparatus of Hart U.S. Pat. No. 4,092,950, the weld joints must be thoroughly cleaned to provide a proper surface for receiving the coatings.
The basic method of cleaning the internal weld joints of an internally coated pipeline, of the type described above, has previously involved a spinning wire brush of the type shown in Hasegawa et al U.S. Pat. No. 3,967,584 issued on July 6, 1976; this method, however, is difficult to control, the operation generally affects the previously applied mill coating and the cleaning itself is inferior to the cleaning effected by sand blasting or grit blasting. Attempts have been made and proposed to abrasively blast the internal weld joints manually, and sometimes automatically but these attempts so far have met with little success. As far as sand blasting or grit blasting itself is concerned, a device for abrasive-blast cleaning of the end of a pipe prior to welding is shown in Hart U.S. Pat. No. 3,972,149 issued on Aug. 3, 1976.
In the present invention, after the grit blast weld cleaner has been properly located over the weld joint, and after the grit blast cleaning operation has continued for a period of time, the weld joint cleaner is caused to oscillate longitudinally with respect to the weld joint. The present inventors are not aware of any prior art device which involves an oscillation of the weld joint cleaner with respect to the weld joint.